Various fiber optic harnesses heretofore have been used in a variety of applications. Harness constructions have been as simple as a specific length of fiber optic cable with a single connector or other termination device on each end. A typical single element cable comprises an optical fiber consisting of a light conducting core together with an integral cladding that is used to convey an optical signal. The optical fiber is surrounded by a tubular protective buffer which provides protection for the relatively fragile optical fiber. Usually, the protective buffer tightly encapsulates the clad optical fiber core in much the same way that electrical insulation typically encapsulates a conventional electrical wire conductor, this essentially restricting any movement of the optical fiber relative to the buffer. However, it is also known to use a buffer that loosely surrounds the optical fiber with sufficient clearance to permit some limited movement of the optical fiber relative to the buffer.
Fiber optic cables also have included a strength member that extends along the length of the cable for carrying the mechanical loads to which the cable may be subjected, thereby to prevent the optical fiber from being stressed to a point of degraded performance. The strength member usually is a flexible, relatively inextensible element or elements such as, for example, aramid or fiberglass fibers.
The buffered optical fiber and, if provided, the strength member are surrounded by an outer covering or jacket which functions to protect the interior components of the cable from the environment, e.g., from abrasion, water, oil, etc. The jacket may be formed by a heat-shrunk or extruded tube which holds together the interior cable components with a tight fit, or the jacket may be in the form of a sheath of woven or braided material wrapped around the interior components of the cable.
More complex harness configurations have been provided such as a fiber optic cable including multiple optical fibers within a common tubular protective buffer or a cable with multiple optical fibers each having its own tubular protective buffer bundled with a common strength member within an outer jacket. Still other harness configurations include multiple cables contained within a harness jacket, each cable having its own protective buffer, strength member and jacket along with an optical fiber. At the ends of the cables, connectors are installed for connecting the cable ends to other optical devices such as other harnesses, optical components, etc. The connectors may be separate and individualized, one for each optical fiber, or they may be multiple contact or channel connectors, wherein optical contacts on the ends of multiple optical fibers are mounted together in a common connector housing.
In more complex harness configurations wherein the number of locations to be interconnected by a single harness may be three or more, electrical wiring harness constructions have been emulated. In a typical harness construction, fiber optic cables each consisting of an optical fiber, buffer, strength member and jacket are routed along respective branches between respective locations. At the branch ends the fiber optic cables are terminated by respective connectors.
In many of the applications in which fiber optic harnesses may be used, such as in aircraft systems, the weight and bulk of the harnesses are important considerations. It would be advantageous to provide a fiber optic harness construction having reduced weight and bulk, while still achieving desired performance, strength and durability characteristics.
Another problem associated with known fiber optic harnesses of any complexity is the difficulty of repairing the harness should one or more of the fiber optic circuits therein be found defective after assembly or become damaged in use. To repair the fiber optic harness, in many cases the harness would have to be disassembled and removed from its installation site, after which the outer jacket would be stripped or cut away to permit replacement of a defective or damaged optical fiber and/or protective buffer. After the replacement had been effected, a new jacket would then have to be reapplied. Consequently, the repair procedure could be a relatively time consuming and costly venture, and in many instances would dictate scrapping the harness rather than attempting to repair it. It would be advantageous to provide a fiber optic harness and method that facilitates repair of one or more fiber optic circuits in the harness.
Another consideration is that of maintaining accurate alignment between the optical contacts in one connector with corresponding contacts in a mating connector. A problem encountered in the past is that mechanical loads acting on the harness have placed stresses on the contacts that could disturb the optical alignment, as by tilting one contact relative to its mating contact, and thereby cause undesirable optical transmission losses. Consequently, it would be advantageous to provide a connector and harness interface wherein the contacts are isolated from mechanical loads acting on the harness.